sized correctly?

[forbaron14]

I had a ac system replaced end of season last year and recently had to turn it on During this heat wave in New Jersey. Old system was A 3 ton and was replaced with same size rheem unit inside and out with new duct work.
I have noticed that this unit can not keep up with the outside temperature and is continually running for hours,even after temps dropped today. My old unit did fine with with out long run times 10 years old
model # of units (rand -036jaz) condenser
(rhla-hm3617ja) air Handler
My house is 1868 sq ft single story with sun all afternoon on house.

Thanks for responses

[Jay 41]

How much duct work was replaced with the new unit , and why? Could be a number of reasons. Are you comparing the new unit to the old unit at same out door temps., or is it unusually hot there? Was a manual J done to size the unit?

[Twilly]

Twilli says were techs NATE and RSES and EMS and did they have a minimum of a GED?

[forbaron14]

Hi jay
Duct was replaced because it was the fiber board and as it turned out it was loaded with mold I guess because of problem I started having with a-coil leaking gas and freezing up .and no he did not do a manual J . As far as temps it does happen yearly where heat and humity really go high usually for a couple of days

[Jay 41]

Personally, I think you should put a call into you company, and ask for a service tech. to come out and look at it. There could be air flow issues, or charge issues, or a combination of things, do you clean or change your filter regularly, this also can be a factor on impropper cooling.

[forbaron14]

I did call and he came out to check freon he actually removed some he also changed wire tap on motor to increase speed and everything else is brand new filter included. Thats why I thought unit maybe to small

[captube]

no he did not do a manual J . As far as temps it does happen yearly where heat and humity really go high usually for a couple of days

Even if he had done man.j it would not be designed for 2 days of weather.

[Jay 41]

I did call and he came out to check freon he actually removed some he also changed wire tap on motor to increase speed and everything else is brand new filter included. Thats why I thought unit maybe to small

If that's the case, captube is probably right, and you'll be fine during a normal cooling season.

[dan sw fl]

Hi jay
Duct was replaced because it was the fiber board and as it turned out it was loaded with mold I guess because of problem I started having with a-coil leaking gas and freezing up .and no he did not do a manual J . As far as temps it does happen yearly where heat and humidity really go high usually for a couple of days

I thought it was near 98'F in NJ last weekend.

I believe That is more than Extreme in comparison to design temperature.

[udarrell]

Newark NJ, summer design 91db 73wb around 45% RH.
Atlantic City NJ, 89db 74wb. 48 or 49% RH.

Was new duct system sized correctly?
Low airflow can kill A/C Btu/hr performance!
According to psychometrics, Two Ton 800-cfm will usually deliver 2-ton cooling even with 3-ton A/C equipment!

What SEER Rating is the new A/C equipment?
It seems the higher the SEER the larger the coil ratio to the compressor capacity for a specific nominal tonnage. However, they seem do do fairly well.

There usually are things you can do to reduce the heat-gain in your home that will reduce energy use year round. - udarrell

[key1cc]

Low airflow can kill A/C Btu/hr performance!


My outside thermometers temp in Princeton, NJ actually hit 101 in the shade!!

Is there a down side to having the CFM changed from 400 to 350 per ton (via dip switches) if the 350 provides sufficient air flow and cooling?
Key1

[RyanHughes]

Less sensible cooling and airflow and more latent cooling (humidity removal). 400 is probably a good setting for Princeton (350 is for areas of high humidity, like FL). Unless you are having issues with humidity at 400, I wouldn't change it.

[key1cc]

Less sensible cooling and airflow and more latent cooling (humidity removal). 400 is probably a good setting for Princeton (350 is for areas of high humidity, like FL). Unless you are having issues with humidity at 400, I wouldn't change it.

It gets very humid here...it just doesnt stay humid as long as it does in florida. I had originally been set up on 400 CFM for the past month, But the HVAC tech guy assessing my ducts today changed it to 350CFM and did a room by room air balancing..... based on me telling him which room were cold and which were hot....no equipment other than a static pressure guage so i am a little suspicious and wanted to make sure no isues with the flow being to low. He finished this morning and the house has been comfortable all day in 95 degree weather.
Key1